The present invention is directed to a started motor for locomotive, and more particularly to a started motor including an improved, robust end casing for carrying an elongated needle bearing. The needle bearing may be in the form of a single roller bearing or multiple roller bearings. The present invention starter motor provides for a higher reliability system for heavy duty, high torque cranking applications with greater critical equipment uptime.
Locomotive engines are generally comprised of large, multi-cylinder diesel engines. When a diesel engine is started, its crankshaft must be rotated at a speed sufficient to compress the air in the cylinders to a pressure at which its temperature is sufficiently high to ignite fuel injected into the cylinders. Fuel may only be supplied after the starter motor has raised the speed of the engine above a predetermined value. Due to the unavoidable leakage of some air past the piston rings, it is essential that the engine be rotated at a high rate of speed, which requires a substantial power output from the starter motor. As a result, the amount of wear to the starter motor is generally significant, causing it to have a short lifespan in comparison to the diesel engine.
Failures of prior art starter motors in the field are generally due to length of service wear. For example, the prior art locomotive starter motor design commonly referred to as the 50MT 32 Volt Locomotive Starter Motor manufactured by Delco Remy, Inc (Pendelton, Ind., USA) was designed for intermittent duty. The prior art starter motor uses a bronze bushing, situated in the drive end of the starter assembly, as the stationary wear surface for the rotating shaft. For its original intended use of relatively few starts a day, the bronze bushing sufficed. However, with environmental regulations demanding train engine shut down when not in motion, the engine must be restarted several times a day. This causes the bronze bushing to be exposed to extensive wear, which usually occurs in an egg shape because the load is applied towards the closed side of the housing cranking cycle after cranking cycle. As a result of such bushing wear, the starter pinion does not correctly mesh with the engine ring gear, resulting in wearing out of the ring gear or damage to both the starter and ring gear.
In modern environmentally challenged diesel engine technology, greater demands on engine brings about greater demands on the starting technology. Today's engine requires significantly more starts and stops (e.g., 10 times per day as compared to 3.5 times per day). The need exists for a longer lasting starter motor, and specifically for a new bushing, which was the main wear item that generally caused the need for replacement. Therefore, it is an object of the present invention starter motor to provide for a higher reliability system for heavy duty, high torque cranking applications with greater critical equipment uptime.
Previous attempts have been made to strengthen the needle bearing and end casing. In such attempts, a higher capacity bearing was applied. The higher capacity was generally achieved by increasing the cross-sectional diameter and area of the needle bearing and associated housing parts. It was thought that by increasing the cross-sectional diameter and area of all parts, wear would be decreased and the needle bearing would have a longer lifespan. However, when this higher capacity needle hearing was applied to the starter motor discussed above, it caused the engine to fail. Specifically, the needle bearing and associated starter motor housing did not meet the size constraints of the locomotive. Therefore, it is an object of the present invention to not only provide for a higher reliability system, but to also meet the size constraints of the locomotive engine.